The present invention relates to an apparatus and method of locating defects, discontinuities, nonconformities and the like (collectively, locations of interest) within objects such as microcomponent devices using ultrasonic technology. More particularly, the present invention relates to an apparatus which comprises a pulse-echo (PE) mode transducer and a through-transmission (TT) mode transducer arranged around a microcomponent in order to introduce ultrasonic sound waves for inspection of the devices to find locations of interest therein.
Ultrasound has long been used for a variety of applications. An example of one such use is in the medical field to obtain two-dimensional soft tissue images. Ultrasound is also widely used in the semiconductor industry (i.e., component testing). For example, two frequently used techniques for non-destructive ultrasonic inspections are pulse-echo mode and through-transmission mode. The PE mode uses a single ultrasonic transducer to launch an ultrasonic impulse into the component to be inspected, and also to receive the reflected echoes. The TT mode uses two transducers facing each other, but on opposite sides of the component to be inspected. In the TT mode, one transducer launches the ultrasonic impulse, while the other transducer receives energy that is transmitted through the component.
Images created using these two techniques contain different types of information regarding the component under inspection, and therefore it is often useful to perform both types of inspection. Nevertheless, two separate inspections are normally required because these two techniques require different connections of the transducers to the ultrasonic instrument (Pulser/Receiver or P/R). I have recognized that this involves considerable additional expense and inspection times, both of which are undesirable when manufacturing components in large batch runs.
Furthermore, in some applications, a single PE image does not provide complete information, because internal structures in the component under inspection may "mask" structures at a greater depth. In this case, it is useful to examine the component using the PE mode from the opposite side as well, so that the two PE images permit a more complete analysis of the component. However, this approach also involves additional expense in using conventional inspection equipment.
U.S. Pat. No. 5,684,252 describes a method and apparatus for non-destructive ultrasonic inspection of integrated circuits or other electronic components laid out in a fixed pattern on a liquid-permeable tray using the above previously described method. I have also recognized that this method lacks the advantages of the present invention because it fails to reduce total manufacturing times by performing simultaneously inspections for defects. Thus, this method also entails high manufacturing costs due to the need to perform dual inspections.